1. Field of the Invention
The present invention relates to an apparatus for the thermal binding of sheets, more specifically for the binding of sheets by a binding element having a binding back on which an amount of glue, which melts under the influence of heat, is provided.
2. Description of the Related Art
It is known that such apparatus mainly consist of a support on which a binding element with a binding back may be placed and a heating element co-operating with the support or forming part thereof. When the heating element is turned on, the binding back heats up, the glue melts and the sheets to be bound are penetrated by the glue.
It is also known to equip these apparatus with detection means to detect the presence of a binding element in the apparatus and with control/switching means which, on the one hand, is connected to the detection means and, on the other hand, is connected to the heating element to switch it on and/or off in such a way that the binding cycle takes place more or less automatically.
In the known embodiments, these detection means consist of an optical eye which is applied sideways above said support in such a way that the presence of a binding element on the support may be detected.
These known embodiments, however, have several disadvantages.
A first disadvantage is that normal operation may be disturbed by dirt, such as dust, material remainders and such like which end up in the apparatus in front of the optical eye.
A second disadvantage is that the presence of the optical eye disadvantageously influences the width of the device. In the case of a plural apparatus, in other words one with several supports applied one next to the other, the possibility of using such an optical eye, and thus the possibility of automating the apparatus, is nearly excluded.